In schistosomiasis the parasite egg is crucial in both pathology and epidemiology, but schistosome reproductive biology is still porrly understood. In unisexual infection in animals, male Schistosoma mansoni develop normally, but females in all-female infections remains stunted and immature. It is likely that chemical mediators are transferred from male to female, entirely apart from insemination. In a closely related parasite, Schistosomatium douthitti, unisexual females can mature and produce viable ova; and the males of this species can induce maturation and oviposition in female S. mansoni. We propose to characterize the putative mediators, their production, transfer, and action. Unisexual and bisexual infections of both species, plus crossed infections, will be established in mice and hamsters. Worms will also be grown in vitro in the same combinations. Worms will be incubated in various ways in labelled compounds, including tryosine (which concentrates in vitelline glands and eggs) and proline (which is reported transferred from male to female), various other precursors, and lipids. Tegumental membrane surface proteins will be labelled with lactoperoxidase and Bolton-Hunter reagent and extracted from male and female worms to determine whether these differ with stage of development and condition of pairing. Artificial worms, "female surrogates" have been developed: these are clasped by males and will be u sed to absorb exuded materials and release them for late analysis. Special study will be made of a protein recently reported to synthesized by male S. mansoni and transferred to the females. Basic analytic methods will include morphological and histological study, 2-dimensional polyacrylamide gel electrophoresis, autoradiography of organisms, fluorography of gels,a dn scintillation counting. The purpose of the study is to understand the relationships of male to female Schistosoma mansoni as a preliminary to control of egg production.